<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
       
        .big{
            width: 400px;
            height: 400px;
            background-color: aqua;
            position: relative;
            z-index: 9999;
        }
        .small{
            width: 200px;
            height: 200px;
            background-color: black;
           position: relative;
            /* z-index: 9999; */
            left: 0px;
            z-index:9999;
        }
        .small1{
            width: 300px;
            height: 300px;
            background-color: brown;
            position: absolute;
            z-index: 8888;
            top: 10px;
        }
    </style>
</head>
<body>
   <div>登陆成功</div>
<script>
     
</script>
</body>
</html>